Friedel-Crafts alkylation and acylation reactions of organic compounds have been commonly performed with Lewis acid catalysts. However, the use of Lewis acid catalysts in commercial practice has presented problems of the catalyst being corrosive, difficult to recover and the generation of hazardous waste.
Examples of such reactions are described in the text by P. Bruice, Organic Chemistry, 4th edition, Prentice Hall, 2004, pg. 612 and following. A common catalyst employed in both alkylation and acylation reactions is the Lewis acid, AlCl3. Although AlCl3 is referred to as a catalyst in the true sense, it is not. It requires stoichiometric amounts of AlCl3 since it actually forms a complex with the reactant, that subsequently requires its removal from the reaction mixture by either an acid or base hydrolysis. Such a procedure is costly and, in the process toxic waste is generated which must be disposed of. Other Lewis acid catalysts have been investigated which include zeolites as disclosed in U.S. Pat. Nos. 4,547,605 and 4,717,780. Although the zeolites are effective Lewis acid catalysts, their use is often limited by the pore size of the zeolite which inhibit large sterically hindered molecules from reaching the active site within the zeolite.
Numerous Lewis acid catalysts have been disclosed which include both transition and non-transition metals as disclosed in U.S. Pat. Nos. 4,414,406 and 6,184,418, however often the catalysts are difficult to prepare or exhibit chemical reactivity that limits their use. Other disclosures include the utilization of mixed catalysts as described in U.S. Pat. No. 5,750,455.
Although much effort has been made to develop more effective catalysts for both alkylation and acylation of organic compounds there is a need for more effective catalysts that do not have the inherent problems of the ones currently employed. An ideal catalyst would be one that functions as a heterogenous catalyst, easily removed from the reactants and products, chemically and thermally stable, and readily available or easily prepared.